Fan



July 19, 194 H. GEISSLER ET AL FAN Filed Jan. 2, 1948 & Fus. 1

INVENTORS .A enry Ge Ass /e r and BY Cass/c Patented July 19, 1949 FAN Henry Geissler, Sharon, and John Cassie, Dedham, Mass, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 2, 1948, Serial No. 60

4 Claims. 1

This invention relates to fans having axial inlets, and relates more particularly to duct connections to the axial inlets for supplying secondary air thereinto.

For maximum performance, the axial inlet of a fan must be nicely streamlined with no obstructions to gas flow extending thereinto. However, for some duties, it is necessary to supply secondary air into a fan inlet through a supply duct; and, in the past, such supply ducts, when not used for supplying secondary air, have extended into the fan inlets and have obstructed the flow thereinto. An example of such a duty is the supply of air through an air heater for the combustion chamber of a steam-power plant. The air supplied by the fan is drawn from the apparatus room in which the fan is located, and blown through the interiors of heat-exchange tubes, over the exteriors of which, the flue gases of the plant pass. At low plant loads, the temperature of the inlet header sheet of the air heater falls below the dew point temperature of the corrosive vapors of the flue gases resulting in the condensation of such vapors on the header sheet with resulting orrosion. Accordingly, it has been the practice at low lant loads to recirculate heated air from the outlet of th air heater into the inlet of the fan for maintaining a large volume of heated air through the heater. Recirculation ducts have extended into the inlets of the fans and have interfered with the flow of air thereinto when no recirculation was required.

An object of this invention is to provide a duct connection to the axial inlet of a fan which does not interfere with the flow of primary air thereinto when there is no flow of secondary air through the duct connection.

Fig. 1 is a side elevation of a centrifugal fan connected to an air heater for a steam-power plant, and embodying this invention, a portion or a side wall of the air heater being removed, and

Fig. 2 is a sectional View along the lines 2-2 of 1, with the lower portions of the side walls of the recirculation ducts at the fan inlets, being removed.

The centrifugal fan It having the opposed axial inlets H through which air is drawn from the apparatus room in which the fan is located, has its outlet 52 connected through the transformation duct I3 to the air inlet of the air heater M.

The air heater I4 consists of a nest of tubes 15 through which the air from the fan passes, and has the duct l6 through which the flue gases from the power plant are supplied to flow over the exteriors of the tubes for heating the air passing therethrough. The heated air from the tubes passes through the supply duct [9 through the combustion chamber of the plant.

The recirculation duct 20 has its inlet connected at 2i to the duct I9 at the downstream side of the heater I4, and has the two branch ducts 2 connected thereto above the fan. The ducts 24 extend down to, and contact, the fan casing, the outer side walls 25 of the ducts 24 extending alongside the side Walls 2-5 of the fan casing. The lower ends of the upper portions of the inner side walls 21 of the ducts 24 (the walls opposite the duct walls 25) contact the upper portions of the side walls 26 of the fan casing in alignment therewith, and the casing side walls 25 below the walls 21, form the inner side walls of the ducts 24 opposite the outer side walls 25 of same.

The lower portions 3'0 of the outer side walls or the ducts 24 are pivoted at 3| to the lower ends of the outer side walls 25 and are arranged to swing inwardly between the end walls 32 of the ducts 24, from the position shown by the continuous lines of Figs. 1 and 2 to the position shown by the dashed lines of Figs. 1 and 2. The position of the duct wall portions 38, shown by the continuous lines of Figs. 1 and 2, is the position these duct wall portions take when the lower portions of the ducts 2d are fully open for the supply of recirculated air into the fan inlets. At such time, as illustrated by Fig. 2, the wall portions 3il are spaced from the fan inlets for per mitting the unrestricted flow of recirculated air through the ducts into the fan inlets. As illustrated by Fig. 1, the lower ends of the duct wall portions 39 have interior portions formed in circular arcs co-axial with the fan inlets, thus pro- Viding equal distribution of air in the upper portions of the fan inlets which are overlapped by the duct wall portions 39.

The position of the duct wall portions 30, shown by the dashed lines of Figs. 1 and 2, is the position they would take when no recirculation is required and the outlets of the ducts 24 are therefore closed off. In this position, the duct portions 38 substantially line up with the converging inlet walls 49 of the fan so that the air from the apparatus room will flow smoothly over the surface of same into the fan inlets without providing any appreciable disturbance in air flow.

The damper ll may be provided in the duct inlet through s d a l i idi 20 for varying the volume of recirculated air when this is desired.

In operation at reduced plant loads when reduced air volumes would be required for combustion, an operator would adjust the duct por- 5 tions 36 to the positions shown by the continuous lines of Efigs. 1 andz, wllgrfibya he recirqulated i Wa d Q J YQQ Y tliei an ink-tarmgether with the primary air from the apparatus room. When the plant load increases to the 10 point where no recirculation is required, the duct 7 lower portions 30 are moved inwardly against the inlet walls 40 so that they do RQt ql st1;p, Qt-;the flow of primary air into theiia inlets.

While one embodiment qf the ipvgp-tion has F15 been described for the purpose of illustration, it should be understood that the invention is lgpt limited to the exact apparatus and arrangement illustrated as modifications thereof may he 511g?- gested by those skilled in the art, without de- 20 par u from th s en 9 t e inve tio w at'i tc i.

n w th a an ax a h p m. inlet ng al smile duct for supplying secoh ary .lsa d du t h lvin tn vqtcd trai iw hij aiiils ah f 9 Pos t on 1 wh ch i i sna es from a nl an rii l ans 'i h qh i badvso n .al snm n with a 2. The combination of claim 1 in which the pivoted wall has in its end opposite its point of pivot, a circular are which is co-axial with the inlet when the pivoted wall is adjusted to said one position.

3. The combination with a fan having an axial inlet through which primary air is drawn,

- i s adjustable to one position in which it contacts said air guiding wall and extends substantially in alignment with same, and which is adjustable to another position in which it is spaced from said inlet and overlaps same.

Th c mb natm as .slaimes in c im 3 in whi h t n i sndrn rtipn 0 th d t a in it end oppos it Po nt Q pivot a c u r which is co-axial-withsaid inlet when the pivoted end portion of the duct is adjusted to the position ,in which it i s spaced from the inlet.

GEISSLER- AJQHZ QASSIE- :N t effi e n e cited- 

